Oxide epitaxial isolation

Abstract

Non-volatile memory cell structures are described that are formed by a method including forming a first oxide layer on a horizontal strained substrate, forming at least one first recess through the first oxide layer to the strained substrate, and forming at least one vertical epitaxial structure in the recess. A crystal lattice of the vertical epitaxial structure is aligned with a crystal lattice of the strained substrate.

Description

TECHNICAL FIELD[0001]The field generally relates to manufacturing of integrated circuits, and in particular to forming vertical epitaxial structures for non-volatile memory cells.BACKGROUND[0002]Integrated circuits are often formed using fabrication steps that include diffusion processes. Photolithography is one method used to diffuse impurities into silicon to create regions of differing doping densities. Diffusion processes can leave impurity concentrations that make it difficult to manage concentration profiles and can result in lower resistivities which lead to less than optimal breakdown voltages for isolating structures.[0003]Epitaxial or “epi” layers have a much lower level of impurities than diffused layers. Epi layers are layers of semiconductor material having the same crystalline orientation as the host substrate on which it is grown—i.e., the epi layer is a single-crystal layer having a constant doping profile (unlike that created by diffusion or implantation) which is n...

AI Technical Summary

Benefits of technology

This approach enables the fabrication of non-volatile memory structures with reduced feature sizes and enhanced isolation, preventing leakage current and allowing for precise control of parasitic capacitance, thereby improving the performance and efficiency of integrated circuits.

Problems solved by technology

Diffusion processes can leave impurity concentrations that make it difficult to manage concentration profiles and can result in lower resistivities which lead to less than optimal breakdown voltages for isolating structures.

Processes that create a single-crystal epitaxial layer from deposited material are somewhat complex and involve the use of a “seed crystal” that allows an annealing process to align the crystals of the deposited material to create a single-crystal material from deposited (non-single-crystal) material.

One concern is that the method of forming the epi structure after the insulating oxide has been thermally grown and creating the active regions using epitaxial growth may result in anomalous tunneling characteristics at the epi / oxide interface.

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